From f9d0e5daa058f0cf4caa8edad0dfa2a3a390f1b0 Mon Sep 17 00:00:00 2001 From: Jian J Wang Date: Wed, 6 Nov 2019 21:13:32 +0000 Subject: [PATCH] MdeModulePkg/DxeIplPeim: reserve page 0 for NULL pointer detection When a boot loader examines the memory map, it can see that location 0 is available memory. If it chooses to use that memory, and PcdNullPointerDetectionPropertyMask is enabled, use of memory in page 0 will cause an exception. This does occur when running the memtest86 program. Leaving page 0 available is for legacy support purpose. Since we have deprecated the support of legacy, the solution is just reserving it so that it cannot be allocated for other uses. Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1885 Cc: Dandan Bi Cc: Liming Gao Cc: Ray Ni Cc: Hao A Wu Cc: Sean Brogan Signed-off-by: Jian J Wang Reviewed-by: Ray Ni --- MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c | 4 ++++ MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c | 4 ++++ 2 files changed, 8 insertions(+) diff --git a/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c b/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c index 172d7cd1c6..6e8ca824d4 100644 --- a/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c +++ b/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c @@ -246,8 +246,12 @@ HandOffToDxeCore ( EFI_PEI_VECTOR_HANDOFF_INFO_PPI *VectorHandoffInfoPpi; BOOLEAN BuildPageTablesIa32Pae; + // + // Clear page 0 and mark it as allocated if NULL pointer detection is enabled. + // if (IsNullDetectionEnabled ()) { ClearFirst4KPage (HobList.Raw); + BuildMemoryAllocationHob (0, EFI_PAGES_TO_SIZE (1), EfiBootServicesData); } Status = PeiServicesAllocatePages (EfiBootServicesData, EFI_SIZE_TO_PAGES (STACK_SIZE), &BaseOfStack); diff --git a/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c b/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c index 2867610bff..f465eb1d8a 100644 --- a/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c +++ b/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c @@ -36,8 +36,12 @@ HandOffToDxeCore ( EFI_VECTOR_HANDOFF_INFO *VectorInfo; EFI_PEI_VECTOR_HANDOFF_INFO_PPI *VectorHandoffInfoPpi; + // + // Clear page 0 and mark it as allocated if NULL pointer detection is enabled. + // if (IsNullDetectionEnabled ()) { ClearFirst4KPage (HobList.Raw); + BuildMemoryAllocationHob (0, EFI_PAGES_TO_SIZE (1), EfiBootServicesData); } // -- 2.39.2